Doh! another knock sensor story

So my 2001 TA threw that damn p0332 code. I thought, alright I can handle it. Buddy and I undertook the challenge and completed the job, which took way to long, like 8 hours (we could probably do it again in under 2 now though). We replaced both knock sensors and the wire harness (in addition to the oil flow sensor and fixing a vacuum line).

After the repairs, I made it a whole 120 miles before the check engine light came back on with the same code. So frustrated right now. Any thoughts on where to go next would be appreciated.

Also, the scanner gave me a whole bunch more info then just the code. Could someone break the following info down Barney style for me? Anything stick out?

Fuel Syst 1 CL
Fuel Syst 2 CL
Calc Load (%) 9.8
ECT (degree F) 167
STFT B1 3.9
LTFT B1 19.5
STFT B2 -0.7
LTFT B2 19.5
Map (inHg) 12.9
Eng RPM 1833
Veh Speed MPH 78
MAF (lb/min) 3.527
TPS (%) 14.5

what brand knock sensors did you use? I went through 3 different ones from autozone before i finally just gave up and went with ac delco. the store brands would last about 4 days and throw a code again, after the delcos its been all good.

did you made sure the harness wire did not got pinched between the engine and the intake? if it is not then i have to say it might be the sensors. when i did mine i used the ac delcos also and not a single problem.

yeah i just replaced mine, and the harness, made it about 150 miles and threw another code, one of mine was a delco, not sure about the other one

Your long term fuel trims are way out of whack. Have you altered the MAF or are you running an aftermarket MAF?

No idea - Fuel Syst 1 CL
No idea - Fuel Syst 2 CL
Engine load - Calc Load (%) 9.8
Engine Coolant Temp - ECT (degree F) 167
Short Term Fuel Trim (driver side) - STFT B1 3.9
Long Term Fuel Trim (driver side) - LTFT B1 19.5
Short Term Fuel Trim (passenger side) - STFT B2 -0.7
Long Term Fuel Trim (passenger side) - LTFT B2 19.5
Manifold Air Pressure - Map (inHg) 12.9
Engine Revolutions Per Minute - Eng RPM 1833
Vehicle Speed - Veh Speed MPH 78
Mass Air Flow Sensor - MAF (lb/min) 3.527
Throttle Position Sensor (0=closed, 100= wide open) - TPS (%) 14.5

I pinched the harness on the front sensor between one of the little nubs on the LS6 valley cover and intake on my engine. I had a solid ground on one side of my harness because of it. I fixed mine over a month ago. One thing you can do is unplug the harness and check the resistance on both terminals of the harness. I had 1000 ohm resistance on the rear sensor and 0 resistance on the front sensor. I knew I had a grounded sensor at that point. It was a fairly easy fix. I had weatherpack terminals and the GM tool and was able to repair the harness rather than buy a new one. I verified I had 1000 ohms on both sides before and after I re-installed the intake. Do this easy check first. Inside of ten minutes it may give you a better clue about the condition of the harness or sensors.

I didn't use AC Delco, I went with BWD knock sensors.

I was pretty careful about the harness when we first put the Intake back on, but I didn't tape the wires down. We did shift the intake around a bit before bolting it down, so I'm not 100% confident that the wires aren't pinched. I figured that if I pinched the wires though, I'd be throwing a code on both sensors and not just bank 2.

Great idea on checking the resistance to the sensors. Wish I'd thought of it, thanks.

Jeff, as far as I know its a stock MAF. I haven't messed with it, but I did buy the car used so there's no telling what used to be on it. How do I go about getting the long term fuel trim adjusted? What should the long term be reading?

Thanks for the help.

Ideally, the trims should be running near zero but anywhere within a range of +/- 5 is probably acceptable. Trims running at or about zero mean that the engine's air/fuel ratio is about spot on. Positive trims mean that the PCM is adding fuel and negative trims mean that it is subtracting fuel. Generally speaking, closed loop fueling is controlled by a combination of airflow metering through the MAF and feedback from the front O2 senders.

It's all well and good to virtual test a problem. I'm old school. Once I knew I had a problem I broke out my meter and physically checked the potential on the leads. It's very easy to pinch just one of the leads. As careful as I am, I pinched the lead for the front sensor. Autotap pointed it out, and I proved it with my voltmeter.

I tried the voltmeter out, but I didn't learn anything. I touched a lead to the harness terminal and the other to the engine block, then switched terminals. No matter what I did I came up with 0 ohms each time. If I did ground the harness out though, I should be showing a check engine light for both sensors not just the rear one. Where did your place the 2nd lead when you tested with your voltmeter?

So what is the difference between the short and long term fuel trim? Can the fuel trim be programed in, or is it something the computer does depending on what its sensors are reading? Could my long term numbers be out of wack because the engine is compensating for the check engine light, the knock senor?

The PCM sets the trims based upon engine sensor feedback. With a scanner, or with something like HP Tuners, you can reset your LTFT's to zero and then see what they do. The knock sensors would simply pull timing, shouldn't have an affect on fueling that I am aware of. I had a MAF issue once that resulted in a lean condition -- this caused the PCM to add fuel based upon feedback from the O2 senders and my long term fuel trims jumped to 25. I would start taking a look at things as there must be a reason for your trims to be so high.

We learned something if your facts are correct. 0 ohms resistance on the terminal going towards the knock sensor tells me there's a solid ground on the lead. Infinite resistance would indicate an open lead. The digital meter would blink or an analog meter would not swing the needle on an open circuit. The expected result would be 1000 ohms like I posted earlier. If both leads test with 0 ohms resistance you've got both leads pinched somewhere. You will show a CEL for the front, rear, or both sensors if there is a problem at any part of the knock sensor circuit. I drove my car over 5000 miles with the CEL light hoping it would go away. It didn't. I finally broke down and fixed it a couple of weeks ago.

I stopped by the autoparts store to rescan the CEL, and now it's throwing 2 codes, p0327 and p0332, both knock sensors. That seems to confirm the zero resistance I found with the voltmeter too. I should be able to tear the intake off next weekend, hopefully its as simple as fixing/replacing the harness.

I had to go back to another website where I discussed the problem I had. It was just the one P0327 code indicated on my car. I had forgotten that code when I originally posted here. I would order a new harness if I were you since both sensors are indicated. I wrapped my harness with extra rubberized electrical tape before I re-installed my intake manifold.

I'll add some more comments, BTW. Last summer I completed the install of my LS6 in my car. I mashed the front sensor wire when I installed the intake. This was on the new engine. I thought when I removed the intake I would re-install my original LS1 KS harness instead. It was brittle and trashed. If you're trying to fix the original harness, I would say not to bother. Buy a new one. I had weatherpack connectors in store and I was able to repair my LS6 harness although the front lead was about three inches shorter after the repair....

Took another shot at it last weekend. After getting the manifold off, I found that I'd crushed the wires. Replaced the harness again, and so far so good. 350 miles and no CEL, knock on wood. Thanks for the help!

Quote:

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Originally Posted by Wammer

Took another shot at it last weekend. After getting the manifold off, I found that I'd crushed the wires. Replaced the harness again, and so far so good. 350 miles and no CEL, knock on wood. Thanks for the help!

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Hope it worked. But clean your maf and get that thing scanned or tuned because your trims being so far off!

i know this sounds odd, but i had a constant code for a year, replaced the knock sensors and harness, no code for 2 weeks, then it came back intermittent.

Replaced the spark plugs a month ago and its gone for good......just a though

I suggest "DAM around the Sensors"
do a serach.
Johnny